U.S. patent number 4,995,333 [Application Number 07/408,019] was granted by the patent office on 1991-02-26 for sprayed adhesive system for applying a continuous filament of theroplastic material and imparting a swirling motion thereto.
This patent grant is currently assigned to Kimberly-Clark Corporation. Invention is credited to Jeffrey J. Jeanquart, Richard F. Keller, Terry L. Springer.
United States Patent |
4,995,333 |
Keller , et al. |
February 26, 1991 |
**Please see images for:
( Certificate of Correction ) ** |
Sprayed adhesive system for applying a continuous filament of
theroplastic material and imparting a swirling motion thereto
Abstract
A distinctive method and apparatus for forming a substantially
continuous filament of a thermoplastic work material and for
imparting a swirling motion thereto comprises a body member which
has a work material supply passage and a gas supply passage formed
therein. An outlet nozzle section connects to the body member and
has a substantially conically tapered shape. The nozzle section has
a nozzle extrusion passage formed therein in communication with the
work material supply passage. A housing member operably connects to
the body member to delimit a substantially annular gas transfer
zone in fluid communication with the gas supply passage and to
delimit a substantially annular gas outlet passage arond the nozzle
section. The housing member includes an exit section having inner
wall surfaces which substantially parallel the conically tapered
shape of the nozzle section. The inner wall surfaces are in a
selected spaced relation from the nozzle section to define the gas
outlet passage. The housing exit section and the nozzle section are
configured to provide for a selected gas from which imparts the
filament swirling motion substantially without disintegrating the
filament, the apparatus thereby constructed to deposit a
substantially continuous, swirled filament of the work material
onto a selected substrate.
Inventors: |
Keller; Richard F. (Fremont,
WI), Springer; Terry L. (Menasha, WI), Jeanquart; Jeffrey
J. (Neenah, WI) |
Assignee: |
Kimberly-Clark Corporation
(Neenah, WI)
|
Family
ID: |
23614517 |
Appl.
No.: |
07/408,019 |
Filed: |
September 15, 1989 |
Current U.S.
Class: |
118/300; 118/313;
156/291; 156/578; 239/290; 118/315; 156/295; 239/8; 239/296 |
Current CPC
Class: |
B05C
5/02 (20130101); D04H 3/05 (20130101); D04H
3/16 (20130101); B05B 7/0861 (20130101); B05B
7/10 (20130101); Y10T 156/1798 (20150115) |
Current International
Class: |
B05C
5/02 (20060101); D04H 3/02 (20060101); D04H
3/16 (20060101); D04H 3/05 (20060101); B05B
7/08 (20060101); B05B 7/02 (20060101); B05B
7/10 (20060101); B05B 007/00 (); B05C 005/00 () |
Field of
Search: |
;156/291,295,578,167
;239/8,290,296-298 ;264/12 ;425/7 ;118/300,302,313-315 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
909427 |
|
Oct 1962 |
|
GB |
|
WO/04040 |
|
Nov 1983 |
|
WO |
|
Other References
"Application Potential of Controlled Fiberization Spray Technology"
Nonwovens Industry, Jan., 1988 pp. 44-46. .
[Advertisement] Nonwovens Industry May, 1988 pp. 46-49. .
Publication: Adhesive Age; Title: Three Steps in the Evolution
HMPSA Spray Technology; Author: John Raterman; Date: Nov.,
1987..
|
Primary Examiner: Ball; Michael W.
Assistant Examiner: Aftergut; Jeff H.
Attorney, Agent or Firm: Yee; Paul
Claims
We claim:
1. An apparatus for forming a substantially continuous filament of
a thermoplastic work material and imparting a swirling motion
thereto, comprising:
a body member which has a work material supply passage and a gas
supply passage formed therein, said gas supply passage
substantially aligned with and generally radially spaced from a
longitudinal central axis of said body member, and said gas supply
passage having substantially no inclination along a radial
direction toward said central axis of said body member;
an outlet nozzle section which is connected to said body member and
has a substantially conically tapered shape, said nozzle section
having a nozzle extrusion passage formed therein in communication
with said work material supply passage; and
a housing member which operably connects to said body member to
delimit a substantially annular gas transfer zone in fluid
communication with said gas supply passage and to delimit a
substantially annular gas outlet passage around said nozzle section
and in fluid communication with said gas transfer zone, said
housing member including an exit section having inner wall surfaces
which substantially parallel the substantially conically tapered
shape of said nozzle section, and which are in a selected spaced
relation from said nozzle section to define said gas outlet
passage, said gas supply passage, said housing exit section and
said nozzle section configured to provide for a selected gas flow
which imparts said filament swirling motion substantially without
disintegrating said filament, said apparatus thereby constructed to
deposit a substantially continuous, swirled filament of said work
material onto a selected substrate.
2. An apparatus as recited in claim 1, wherein said nozzle section
and said housing member are configured to provide an arrangement
wherein said gas outlet passage is asymmetrically disposed around
said nozzle section.
3. An apparatus as recited in claim 1, wherein said nozzle
extrusion passage has a diameter within the range of about
0.046-0.056 cm.
4. An apparatus as recited in claim 1, wherein said nozzle
extrusion passage has a length-to-diameter ratio of at least about
8:1.
5. An apparatus as recited in claim 1, wherein said nozzle
extrusion passage has a length-to-diameter ratio of at least about
10:1.
6. An apparatus as recited in claim 1, wherein said nozzle
extrusion passage has a length-to-diameter ratio within a range of
about 8:1-12:1.
7. An apparatus as recited in claim 1, wherein said work material
supply passage is substantially aligned with a longitudinal,
central axis of said body member.
8. An apparatus as recited in claim 1, wherein said work material
supply passage is circumferentially inclined at a selected angle
with respect to said longitudinal central axis of said body
member.
9. An apparatus as recited in claim 1, wherein said gas supply
passage has a length-to-diameter ratio of at least about 9:1.
10. An apparatus as recited in claim 1, wherein said gas supply
passage has a length-to-diameter ratio which is within a range of
about 9:1 to 12:1.
11. An apparatus as recited in claim 1, wherein said gas supply
passage is circumferentially inclined with respect to said
longitudinal axis of said body member with said inclination angled
generally along a circumferential direction of said body member at
an angle of not more than about 25 degrees.
12. An apparatus as recited in claim 1, wherein said nozzle section
has a cone angle within a range of about 40-50 degrees.
13. An apparatus as recited in claim 1, wherein said inner wall
surfaces of said housing member outlet passage are spaced from said
nozzle section by a distance within a range of about 0.041-0.046
cm.
14. An apparatus as recited in claim 1, wherein said housing member
comprises a cap member which is removably connected to said body
member.
15. An apparatus as recited in claim 1, wherein said housing member
includes a recess section formed in an outwardly facing surface of
said housing member and surrounding said exit section of the
housing member.
16. An apparatus as recited in claim 15, wherein said recess
section has a radial dimension within a range of about 0.521-0.625
cm.
17. An apparatus as recited in claim 15, wherein said recess
section has a generally circular side wall arranged in a
substantially frusta-conical configuration with a largest diameter
thereof positioned at an outward surface of the housing member.
18. An apparatus as recited in claim 15, wherein said nozzle
section protrudes into said relief section by a selected distance
of about 0.013-0.015 cm.
19. An apparatus as recited in claim 1, further comprising gas
delivering means for providing gas into said gas supply passage of
said body member at a pressure of not more than about 32 psi (about
221 kPa).
20. An apparatus as recited in claim 1, wherein said gas delivering
means is constructed to provide gas at a pressure within a range of
about 12-32 psi (82.7-221 kPa).
21. An apparatus as recited in claim 1, further comprising work
material delivering means for providing work material to said body
member at a pressure of not more than about 1000 psi (6894
kPa).
22. An apparatus as recited in claim 1, wherein said work material
delivering means is constructed to provide said work material at a
pressure within a range of about 250-750 psi (about 1724-5170
kPa).
23. An apparatus as recited in claim 1, wherein said gas supply
passage communicates with said gas transfer zone through an
opening, and said gas supply passage is radially spaced from said
annular gas outlet passage by a spacing distance corresponding to
approximately 0.5-0.9 times an effective diameter of said
opening.
24. An apparatus as recited in claim 1, wherein said gas supply
passage communicates with said gas transfer zone through an
opening, and said gas supply passage is radially spaced from said
annular gas outlet passage by a spacing distance corresponding to
approximately 0.7-0.8 times an effective diameter of said
opening.
25. An apparatus as recited in claim 1, further comprising:
a valving chamber formed in said work material supply passage, said
chamber having a bottom wall section and an open end portion;
a valving member located within said valving chamber;
a valve seating member connected to said body member at said open
end portion of said valving chamber; and
forcing means for resiliently urging said valving member against
said valve seating member to selectively block a flow of material
into said valving chamber.
26. An apparatus as recited in claim 25, wherein said forcing means
provides a closure force which allows displacement of said valving
member from said valve seating member when work material is applied
under a pressure of about 100 psi.
27. An apparatus as recited in claim 25, wherein said forcing means
comprises a spring which engages said bottom wall section and said
valving member.
28. An apparatus as recited in claim 27, wherein said spring
provides a closure force within a range of about 0.25-1.0
pounds.
29. An apparatus as recited in claim 11, wherein said gas supply
passage communicates with said gas transfer zone through an
opening, and said gas supply passage is radially spaced from said
annular gas outlet passage by a spacing distance corresponding to
approximately 0.5-0.9 times an effective diameter of said
opening.
30. An apparatus as recited in claim 11, wherein said gas supply
passage communicates with said gas transfer zone through an
opening, and said gas supply passage is radially spaced from said
annular gas outlet passage by a spacing distance corresponding to
approximately 0.7-0.8 times an effective diameter of said
opening.
31. An apparatus as recited in claim 11, further comprising:
a valving chamber formed in said work material supply passage, said
chamber having a bottom wall section and an open end portion;
a valving member located within said valving chamber;
a valve seating member connected to said body member at said open
end portion of said valving chamber; and
forcing means for resiliently urging said valving member against
said valve seating member to selectively block a flow of material
into said valving chamber.
32. An apparatus as recited in claim 31, wherein said forcing means
provides a closure force which allows displacement of said valving
member from said valve seating member when work material is applied
under a pressure of about 100 psi.
33. An apparatus as recited in claim 31, wherein said forcing means
comprises a spring which engages said bottom wall section and said
valving member.
34. An apparatus as recited in claim 33, wherein said spring
provides a closure force within a range of about 0.25-1.0 pounds.
Description
FIELD OF INVENTION
The present invention relates to a method and apparatus for
applying a selected pattern of work material onto a chosen
substrate. More particularly, the present invention relates to a
method and apparatus for spraying a selected pattern of hot-melt
adhesive onto a moving substrate layer to construct a garment
article, such as a disposable diaper.
BACKGROUND OF INVENTION
In the manufacture of disposable absorbent articles, such as
diapers, feminine care products, incontinence products, and the
like, adhesives have typically been applied in a pattern of
multiple, parallel glue lines which extend along the longitudinal
dimension of the article. Such glue line patterns leave unbonded
gaps between the lines, and the unbonded gap areas tend to have
lower strength and lower integrity. As a result, the article can be
more susceptible to stretching and tearing when adhesive tapes are
employed to secure the article on the wearer, and the article may
be less able to hold together and maintain its structure during
use.
Sprayed and foamed adhesives have also been employed to assemble
together various component layers of disposable absorbent articles.
The adhesives may be thermoplastic-type adhesives or solvent-type
adhesives. For example, see U.S. Pat. No. 3,523,536 to A. Ruffo and
U.S. Pat. No. 4,118,531 to Minetola, et al. Swirled patterns of
adhesive have been employed to construct articles such as shoes.
For example, see U.S. Pat. No. 3,911,173 issued Oct. 7, 1975 to J.
Sprague.
Various air forming techniques have been employed to form nonwoven
fibrous webs. For example, U.S. Pat. No. 4,478,624 issued Oct. 23,
1984 to J. Battigelli, et al. describes a technique which employs a
circular airflow component to help produce a more uniform
distribution of fibers laid onto a foraminous conveyor. U.S. Pat.
No. 2,903,387 issued Sept. 8, 1959 to W. Wade describes a technique
for producing reticulated fibrous webs containing tubular or hollow
fibers of elastomeric material. U.S. Pat. No. 2,950,752 issued Aug.
30, 1960 to P. Watson, et al. describes a spraying technique for
forming relatively long, discontinuous, fine fibers of elastomeric
materials. The fiber-forming liquid is extruded into and within a
primary or high velocity stream of gas as a stream of plastic which
is broken transversely into a plurality of fibers or fibrils before
landing on a collector. U.S. Pat. No. 2,988,469 issued June 13,
1961 to P. Watson describes a further spraying technique for
forming relatively long, discontinuous, fine fibers of
non-elastomeric material. A high velocity jet stream of gas
attenuate and fibrillates a single large-diameter plastic stream
into a multiplicity of fibers and fibrils without the formation of
shot.
Molded articles and preforms have been produced by depositing
fibers into a form and binding the fibers together with a resin
binder. For example, U.S. Pat. No. 3,796,617 issued Mar. 12, 1974
to A. Wiltshire describes a method for making a fibrous preform
which comprises the steps of randomly depositing short reinforcing
fibers on a form, binding the fibers together with a settable resin
binder, and rolling the resin-coated fibers on the form into a
dimensionally uniform porous mat. U.S. Pat. No. 3,833,698 describes
a technique in which chopped fibers are directly deposited in a
localized manner onto the interior surface of a screen form. The
fibers are held in place by an airflow through the screen form into
a vacuum chamber, and the deposited chopped fibers are sprayed with
a heat-curable resin binder. U.S. Pat. No. 3,904,339 issued Sept.
9, 1975 to J. Dunn describes a technique for depositing glass
fibers and curable resin into molds. A spray means for depositing
the resin and fibers is supported on an arm which is pivoted about
a selected axis.
Particular nozzle structures have been developed to form filaments
from thermoplastic, melt-extrudable materials. The nozzles may be
configured to produce a swirling air flow which disrupts the flow
of extruded material into a plurality of fine fibers. For example,
U.S. Pat. No. 4,185,981 describes a technique for producing fibers
from a viscous melt. High-speed gas streams have a component in the
tangential direction of the circular sectional surface of the melt,
and a component which approaches the central axial line of the melt
towards the flowing direction of the melt and then departs from the
central axial line. The melt is continuously flown as fiber in the
flowing direction and outwardly in the radial direction in a vortex
form, which is spiral or helical or both. The fibrous melt which
has flown away is accelerated and drawn into long fibers having a
diameter of 10-100 microns, or short fibers having a diameter of
0.1-20 microns. The fibers can then be accumulated to form a
fibrous mat.
U.S. Pat. No. 2,571,457 issued Oct. 16, 1951 to R. Ladisch
describes a technique in which a cyclone of gas disrupts a
"filament forming liquid" into fibers and/or filaments which may be
collected on a moving belt. U.S. Pat. No. 3,017,664 issued Jan. 23,
1962 to R. Ladisch describes a fiber-forming nozzle wherein a
fiber-forming liquid is spread over the outside wall of a circular
body as a thin film, and wherein a stream of spiraling elastic
fluid rotates at high velocity to draw out fibers which are picked
up from the film of fiber-forming liquid.
U.S. Pat. No. 3,905,734 issued Sept. 16, 1975 to E. Blair describes
an apparatus for continuously making a tube of meltblown
microfibers. The meltblown microfibers are deposited longitudinally
upon a circumferential surface of a mandrel and then are axially
withdrawn from one end of the mandrel tube.
U.S. Pat. No. 3,543,332 issued Dec. 1, 1970 to W. Wagner, et al.
describes a spinning nozzle for spray spinning molten fiber-forming
materials and forming fibrous assemblies such as nonwoven fabrics
and the like. The nozzle includes gas passages which are inclined
so that their axes do not intersect the axis of an extrusion
orifice in the nozzle. Gas streams act to swirl filaments formed
from the fiber-forming material to produce a random expanding
conical pattern as the filaments travel toward a moving
collector.
An article entitled "Application Potential of Controlled
Fiberization Spray Technology", Nonwovens Industry, January 1988,
by J. Raterman describes a process for spraying pressure-sensitive
hot-melts. The process employs a line of spray heads using nozzles
with integral air jets that produce fine monofilaments of adhesive
swirled at high speeds in a helix or spiral pattern.
Conventional spray techniques, such as those discussed above, have
been excessively complex, and have not adequately regulated the
distribution pattern and placements of the sprayed material onto a
substrate. Ordinarily, the sprayed materials are deposited in a
generally random pattern, and there can be excessive overspray and
misplacement of the deposited materials. Where the sprayed
materials are composed of adhesives, such as hot-melt adhesives,
the overspray and misplacement can contaminate the equipment and
require excessive maintenance. For the purpose of applying
adhesives onto a substrate, the conventional techniques have not
provided a sufficiently accurate control over the deposition
pattern and have not been sufficiently flexible or readily
adjustable to accommodate the placement of adhesives onto different
widths of substrate. In addition, the conventional spray devices
have been excessively sensitive to plugging when employed with
viscous liquids, such as hot-melt adhesives.
BRIEF DESCRIPTION OF THE INVENTION
The present invention provides a distinctive apparatus for forming
a substantially continuous filament of a thermoplastic work
material and imparting a swirling motion thereto. Generally stated,
the apparatus comprises a body member which has a work material
supply passage and a gas supply passage formed therein. An outlet
nozzle section, which is connected to the body member, has a
substantially conically tapered shape and has a nozzle extrusion
passage formed therein in communication with the work material
supply passage. A housing member, which operably connects to the
body member, delimits a substantially annular gas transfer zone in
fluid communication with the gas supply passage and delimits a
substantially annular gas outlet passage around the nozzle section.
The housing member includes an exit section having inner wall
surfaces which substantially parallel the substantially conically
tapered shape of the nozzle section, and which are in a selected
spaced relation from the nozzle section to define the gas outlet
passage. The housing exit section and the nozzle section are
configured to provide for a selected gas flow which imparts the
filament swirling motion substantially without disintegrating the
filament, and the apparatus is thereby constructed to deposit a
substantially continuous, swirled filament of the work material
onto a selected substrate.
The invention further provides a method for depositing a selected
pattern of material onto a substrate. Generally stated, a method
for forming a substantially continuous filament of a thermoplastic
material and imparting a swirling motion thereto includes the steps
of supplying a thermoplastic work material to a nozzle section, and
forming a substantially continuous filament of the work material
which exits from the nozzle section. A supply of gas is delivered
to a gas transfer zone through a gas delivery conduit which is
generally aligned along a longitudinal axis of the nozzle section.
The gas exits from the gas transfer zone through a substantially
annular gas outlet passage which is positioned around the nozzle
section. The gas moves through the gas outlet passage and past the
nozzle section to provide for a selected gas flow which imparts the
swirling motion to the filament while substantially avoiding a
disintegration of the filament, thereby depositing a substantially
continuous, swirled filament of the work material onto a selected
substrate.
The invention can additionally provide a distinctive absorbent
article comprising an outer layer, a liquid-permeable inner layer,
and an absorbent body positioned between the inner and outer
layers. A pattern of adhesive is arranged to secure one or more of
the layers to the absorbent body, and is composed of a plurality of
accurately positioned, juxtaposed, substantially continuous,
semi-cycloidal arrays of adhesive extending substantially along a
longitudinal dimension of the article.
The method and apparatus of the present invention can
advantageously provide a more accurate placement of deposited work
material onto a substrate layer, and can provide a more precise
formation of a desired deposition pattern. Since the work material,
such as a molten adhesive, is gas-entrained for a discrete distance
before contacting the substrate web, the adhesive has an
opportunity to cool, or depending on the temperature of the gas,
may be held or maintained at a selected temperature. A cooling of
the adhesive reduces the probability that the web will be exposed
to excessive amounts of heat from the adhesive. The technique of
the present invention can be readily adjusted to accommodate and
control the placement of material onto substrates of various
widths. When compared to conventional devices, the method and
apparatus of the invention can better prevent the undesired upwards
spiraling of the extruded filament onto the nozzle unit, and can
help prevent any resultant plugging of the air passages. Thus, the
technique of the invention can help reduce the amount of overspray
waste and help reduce the maintenance requirements for the
associated production equipment. The invention can further provide
a more effective distribution of adhesive on the applied surface
area of the article, and can thereby provide an article having more
uniform strength characteristics. An article constructed in
accordance with the invention may be perceived by the consumer as
having increased integrity.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more fully understood and further advantages
will become apparent when reference is made to the following
detailed description of the invention and the drawings, in
which:
FIG. 1 representatively shows a side elevational view of the
apparatus of the present invention;
FIG. 1A representatively shows an enlarged view of the region
circled in FIG. 1;
FIG. 2 representatively shows a plan view of an assembly comprising
two nozzle banks;
FIG. 3 representatively shows a side elevational view of the
assembly illustrated in FIG. 2;
FIG. 4 representatively shows a cross-sectional view of an
individual nozzle mechanism;
FIG. 5 representatively shows a cross-sectional view of a plug
assembly employed to adjust the deposition width and pattern
provided by the present invention;
FIG. 6 representatively shows an enlarged cross-sectional view of
an individual nozzle mechanism;
FIG. 7 representatively shows a cross-sectional view of an
alternative configuration of a nozzle mechanism;
FIG. 8 representatively shows a side elevational view of a nozzle
having an inclined gas supply passage;
FIG. 9 representatively shows an end view of the nozzle illustrated
in FIG. 8 taken along direction 9--9;
FIG. 10 representatively shows a deposition array comprising a
semi-cycloidal pattern;
FIG. 11 representatively shows a deposition array comprising a
plurality of juxtaposed, semi-cycloidal patterns;
FIG. 12 shows a schematic representation of the adhesive delivery
system; and
FIG. 13 shows a schematic representation of the heated air delivery
system;
FIG. 14 representatively shows a disposable diaper constructed in
accordance with the present invention; and
FIG. 15 representatively shows a graphic comparison of end seal
strengths provided by conventional bead-lines of adhesive and by
the swirled adhesive patterns of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a distinctive method and apparatus
for depositing a selected pattern of work material onto a selected
substrate, such as the outer cover layer of a disposable diaper.
While the following description will be made in the context of
depositing a hot-melt adhesive, it will be readily apparent to
persons of ordinary skill that other types of adhesives and other
types of viscous, extrudable materials may also be applied by
employing the technique of the invention. Similarly, while the
following description will be made in the context of constructing a
disposable diaper, it will be readily apparent that the technique
of the present invention would also be suitable for producing other
articles, such as feminine care products, incontinence products,
disposable gowns, laminated webs, and the like.
The described embodiments of the present invention are
distinctively constructed and arranged to form a substantially
continuous filament of a thermoplastic work material and to impart
a swirling motion thereto. As a result, a substantially continuous,
swirled filament of the work material can be deposited onto a
selected substrate.
FIGS. 1 and 1A representatively show an apparatus for depositing a
closely controlled pattern of work material, such as hot-melt
adhesive 12, onto a selected substrate, such as web 14. The
apparatus includes a supply means, such as nozzle assembly 10, for
forming at least one, substantially continuous stream of the
material. Gas directing means form at least one gas stream, which
has a selected velocity and is arranged to entrain the material
stream 11 to impart and substantially maintain a relatively precise
swirling motion to the material stream as it moves toward substrate
web 14. Transport means, such as conveyor rollers 15 and 16, move
the substrate relative to the supplying means along a selected
machine direction 27. Regulating means, including pumps 33 (FIG.
12) and pressure control valve 18 (FIG. 13), control the material
stream and the velocity of the gas stream, respectively, to direct
material stream 11 in a selected path toward substrate 14 and
deposit the material thereon to form a substantially continuous,
semi-cycloidal pattern of the material on substrate 14.
Roller 15 may optionally be a constant temperature roll which is
held at a temperature below or above the ambient temperature, as
desired. As a result, roller 15 can operably support and guide web
14, and can also operably cool or heat the web. For example, roller
15 may be a chill roll which is conventionally configured with a
plurality of internal passages, and constructed and arranged to
conduct and transport a suitable liquid coolant therethrough. The
coolant can be cooled by a conventional refrigeration unit to a
temperature of about 18.degree. C., and the circulation of the
coolant through the chill roll operably maintains the outer surface
of the chill roll at a predetermined temperature. The resultant
cooling action provided by chill roll 15 helps prevent excessive
heating of web 14 by the hot-melt adhesive deposited thereon, and
can accelerate the solidification of the adhesive on the web.
A drip plate 25 is located below the position occupied by web 14 as
the web moves over the conveyor rollers and past the location of
nozzle assembly 10. The drip plate is constructed and arranged to
intercept and catch any excess hot-melt adhesive which might be
expelled or drip from the nozzle units 24 during any time that web
14 is absent from the system. The presence of drip plate 25 can
thereby advantageously reduce the contamination of the equipment by
fugitive adhesive, and reduce the amount of system maintenance. In
particular, the presence of drip plate 25 can help prevent
excessive equipment contamination during web splicing operations.
In the shown embodiment, the drip plate is removable for
cleaning.
With reference to FIGS. 2 and 3, nozzle assembly 10 includes a
first nozzle bank 20 and at least a second nozzle bank 22, with the
first nozzle bank spaced a selected offset distance 23 from the
second nozzle bank along machine direction 27 of the apparatus. The
offset distance is arranged and configured to substantially prevent
interference between the deposition patterns formed by each of the
individual nozzle units 24. Each nozzle bank 20, 22 includes a
plurality of spaced-apart nozzle units 24 which are substantially
aligned along a cross-direction 26 of the apparatus. The nozzles of
second nozzle bank 22 are, however, positioned in an interposed,
staggered arrangement relative to the nozzles of first nozzle bank
20. Each nozzle includes an orifice 82 for forming a substantially
continuous stream of hot-melt adhesive 11, and includes a gas
delivery system for forming a selected gas stream which has a
selected velocity and is arranged to entrain the associated,
individual stream of hot-melt adhesive 11 issuing from orifice 82.
The gas stream in distinctively directed to impart a swirling
motion to each material stream 11 as it moves toward web 14. In the
illustrated embodiment, the individual nozzle units 24 within a
particular nozzle bank are substantially equally spaced along the
cross-direction. Alternatively, the individual nozzle units within
a nozzle bank may be unequally spaced, if desired.
FIG. 3 representatively shows a side view of nozzle assembly 10
comprising nozzle plate 32 and transfer plate 44 which are joined
and held together with suitable fastening means, such as bolts 46.
The nozzle plate and transfer plate are formed of a suitable
material, such as metal. In the illustrated embodiment, the nozzle
and transfer plates are composed of heat treated stainless steel. A
suitable gas, such as air, is introduced into nozzle plate 32
through one or more gas inlets 36. In the illustrated embodiment,
there are two individual gas inlets, but more or fewer inlets could
also be employed. A desired liquid, such as a molten hot-melt
adhesive, which is to be applied to web 14, is provided into
transfer plate 44 through liquid inlets 84 and 84a. In the
illustrated embodiment, liquid inlets 84 supply molten adhesive to
nozzles in first nozzle bank 20, and liquid inlets 84a supply
molten adhesive to nozzles in second nozzle bank 22. Each
individual nozzle unit receives adhesive supplied through an
individual inlet. Excess liquid, which is not expelled through
nozzle units 24, is recirculated out from nozzle plate 32, as
discussed in more detail below with respect to FIG. 12. The
recirculation of excess hot-melt adhesive can advantageously
provide improved control over the deposition patterns of adhesive
onto web 14 and can facilitate changes in the system to increase or
decrease the total cross-directional width of web 14 which is
covered by the array of adhesive deposition patterns.
A more detailed illustration of the environment around an
individual nozzle unit 24 is representatively shown in FIG. 4. In
the illustrated embodiment, nozzle plate 32 is configured with a
plurality of nozzle bore holes 48 which extend through the
thickness dimension of the nozzle plate and are suitably positioned
in spaced arrangement corresponding to the desired locations of the
individual nozzle units. Each bore hole 48 has an expanded region
70 of increased diameter located adjacent to one major surface 54
of nozzle plate 32. As a result, the nozzle bore has a stepped
cross-sectional configuration.
Each bore hole 48 is constructed to receive therein a nozzle body
50 which is secured with suitable fastening means, such as bolts 52
(FIG. 2). The nozzle body is constructed of a suitable material,
such as metal or high-strength, temperature-resistant plastic. In
the illustrated embodiment, the nozzle body is composed of hardened
stainless steel.
Nozzle body member 50 includes a stem portion 56 and a head portion
58, and has work material (e.g. adhesive) supply passage 64 formed
axially therethrough. Stem portion 56 includes two circumferential
grooves 60 configured to accommodate the placement of O-ring type
seals 61 composed of a conventional, high temperature elastomeric
material, such as Viton type O-rings, which are produced by Parker
Hannifin, a company having facilities in Lexington, Ky. Grooves 60
extend circumferentially around stem portion 56, and are
constructed and arranged to hold the O-rings in sealing engagement
with the interior wall surface of bore 48. In addition, grooves 60
are axially spaced along the length of stem portion 56, and are
arranged to bracket either side of adhesive return port 62, which
is formed through nozzle plate 32 in fluid communication with bore
48. In the illustrated embodiment, stem portion 56 is necked down
with a reduced diameter at its medial section 66. The medial
section cooperates with expanded region 70 of bore 48 to provide an
annular passageway between the nozzle stem and the side wall of the
bore hole. A gas inlet port 68 is formed through nozzle plate 32
and positioned in fluid communication with expanded region 70 of
bore 48. Gasket member 38 provides a substantially airtight seal
between surface 54 and flange 72. The gasket is composed of a
conventional fibrous gasket material, and is configured to reduce
air leaks caused by irregularities in the mating surfaces arising
from manufacturing machining tolerances.
Head portion 58 of nozzle body 50 includes an annular flange 72
which extends about the head portion and is constructed to seat in
engagement with the outer surface 54 of nozzle plate 32. The head
portion further includes a gas passage 74, which is formed through
the head portion. In the shown embodiment, gas passage 74 extends
axially through the head portion of nozzle body 50 and is radially
spaced from adhesive supply passage 64. The gas passage is
constructed and arranged to be in fluid communication with expanded
region 70 of bore 48.
A more detailed illustration of an individual nozzle unit 24 is
representatively shown in FIG. 6. The nozzle unit includes a body
member 50 which has a work material supply passage 64 and a gas
supply passage 74 formed therein. An outlet nozzle section 80 is
connected to body member 50 and has a substantially conically
tapered shape. The nozzle section has a nozzle extrusion passage 65
therein with the extrusion passage arranged in operable
communication with work material passage 64. A housing member 78
operably connects to body member 50 to delimit a substantially
annular gas transfer zone, such as annular groove 76, which is in
fluid communication with gas passage 74, and delimits a
substantially annular gas outlet passage 63 around nozzle section
80. Housing member 78 includes an exit section 67 having inner wall
surfaces 69 which substantially parallel the substantially
conically tapered shape of nozzle section 80. The inner wall
surfaces are in a selected, spaced relation from nozzle section 80
to define gas outlet passage 63. The housing exit section and the
nozzle section are configured to provide for a selected gas flow
which imparts the desired swirling motion to filament 11
substantially without disintegrating the filament. In particular,
the nozzle unit is substantially free of air currents or other
mechanisms which are arranged to deliberately break the filament
into discrete fibers or otherwise significantly disrupt the
continuity of the swirling filament of work material. Accordingly,
the nozzle unit can advantageously deposit a substantially
continuous, swirled filament of work material onto a selected
substrate.
In the illustrated embodiment, the distal, terminal end of head
portion 58 includes an annular groove 76, which is formed into an
axial end face 86 of the head portion. Groove 76 is configured to
connect in fluid communication with gas passage 74, and to help
provide a circumferential, substantially annular gas transfer zone
around outlet nozzle section 80. The illustrated gas transfer zone
has an axial depth within the range of about 0.050-0.052 inches
(0.127-0.128 cm).
The opening of gas passage 74 into the gas transfer zone provided
by groove 76 is spaced radially outward from gas outlet passage 63
by a selected distance 142. In a particular aspect of the
invention, spacing distance 142 corresponds to approximately
0.5-0.9 times the effective diameter of the opening of gas passage
74 into the gas transfer zone. In the illustrated embodiment,
spacing distance 142 is within the range of about 0.040-0.044
inches (about 0.102-0.112 cm), which corresponds to approximately
0.7-0.8 times the diameter of gas passage 74.
Gas passage 74 is substantially aligned with the longitudinal axis
of nozzle body 50, and in the shown embodiment, comprises a
generally cylindrical bore through the nozzle body. The bore has a
diameter 144 and a length 146. In a particular aspect of the
invention, the length-to-diameter ratio of the gas passage is at
least about 9:1 and is preferably within the range of about 9:1 to
12:1 to provide improved effectiveness. If the length-to-diameter
ratio of gas passage 74 is too small, the nozzle unit may not
impart the desired swirling motion to the filament of work
material.
To provide additional advantages, gas supply passage 74 may
optionally be inclined at a selected inclination angle 148 with
respect to the longitudinal axis of nozzle body 50. In an aspect of
the invention representatively shown in FIGS. 8 and 9, the gas
supply passage is inclined from the axial direction and tilted
along a circumferential direction of the body member at an
inclination angle 148 of not more than about 25.degree..
Preferably, the gas supply passage is constructed to have
substantially no inclination along the radial direction toward the
central axis 160 of nozzle body 50. An inclination of gas passage
74 toward the central longitudinal axis of the nozzle body may
impede the formation of the desired swirling motion of filament
11.
Outlet nozzle section 80 is operably connected to the end of head
portion 58, and in the shown embodiment is integrally formed with
the head portion. Nozzle section 80 has an axially extending
extrusion passage 65 formed substantially along the nozzle
centerline for conducting molten work material therethrough.
Extrusion passage 65 is configured to connect in fluid
communication with supply passage 64, and generally comprises a
cylindrical bore having a diameter 132 and a length 134. To provide
a desired filament of work material, such as hot- melt adhesive,
extrusion passage 65 has a length-to-diameter ratio of at least
about 8:1, and preferably has a length-to-diameter ratio of at
least about 10:1 to provide improved effectiveness. Other preferred
embodiments can be constructed with a length-to-diameter ratio
within the range of about 8:1-12:1. In the illustrated embodiment,
extrusion passage 65 is configured with a diameter of about
0.0305-0.0762 cm. (about 0.012-0.030 in.). Preferably, the diameter
of extrusion passage 65 is about 0.0457-0.0635 cm. (about
0.018-0.025 in.), and more preferably the diameter is about 0.0508
cm. to provide improved performance.
As representatively shown in FIG. 6, nozzle section 80 has a
tapered, substantially conical shape with the apex of the cone
directed toward orifice 82, which is located at the exit from
extrusion passage 65. In the illustrated embodiment, nozzle section
80 has an approximately frusta-conical shape to accommodate the
formation of extrusion passage 65 and to facilitate the formation
of a regular, uniformly shaped outlet opening 82 at the end of the
extrusion passage. The cone angle 136 of the nozzle section is at
least about 30.degree., and preferably is at least about
40.degree.. Also, the cone angle is not more than about 60.degree.
and preferably is not more than about 50.degree. to provide
improved effectiveness. In the shown embodiment, the cone angle is
approximately 45.degree..
The outward, conical surface of nozzle section 80 is substantially
smooth, and is substantially free of any grooves, flutes, guide
channels, vanes or the like which would operate to mechanically
contact and guide the airstream in gas outlet passage 63 into a
swirling motion. It has been found that the distinctive
configuration of the present invention can produce a desired
swirling gas stream without the use of the deflecting or steering
mechanisms typically employed to direct the gas flow.
Housing member 78 to nozzle body 50, and in the shown embodiment,
is threaded onto the nozzle body. The housing member cooperates
with groove 76 to define the gas transfer zone, and cooperates with
nozzle section 80 to define gas outlet passage 63. In particular,
an inner wall surface 69 is configured for positioning in a
substantially parallel arrangement with respect to the conically
tapered shape of nozzle section 80. In the illustrated embodiment,
the inward, conical face of wall surface 69 is substantially
smooth, and is substantially free of any grooves, flutes, guide
channels, vanes or the like which would operate to mechanically
contact and guide the airstream in gas outlet passage 63 into a
swirling motion. Wall surface 69 has a selected spacing 138 from
nozzle section 80. Spacing distance 138 is within the range of
about 0.016-0.018 inches (about 0.041-0.046 cm) and is
substantially uniform over the conical surface of nozzle section
80.
In the shown embodiment, the outward conical surface of nozzle
section 80 and inner wall surface 69 both have the configuration of
a right circular cone, and the axial centerline of nozzle section
80 is substantially aligned with the conical centerline of wall
surface 69 to provide a generally uniform, annular, conical gas
outlet passage 63. The effective length 140 of gas passage 63 is at
least about 0.093 inches (about 0.236 cm), and in the shown
embodiment is approximately 0.115 inches (about 0.292 cm). In
another aspect of the invention, nozzle section 80 may be
asymmetrically positioned with respect to wall surface 69 to
produce a non-uniformly shaped, unsymmetrical gas outlet passage
63. Such a configuration can be employed to produce a gas stream
which entrains filament 11 into a swirling motion but veers the
swirling filament in a direction which is offset or angled with
respect to the longitudinal axis 160 of nozzle body 50. The
configuration where gas outlet passage 63 is asymmetrically
disposed around the nozzle section can, for example, be employed to
selectively configured the composite pattern of hot melt adhesive
deposited onto a substrate.
Gas outlet passage 63 is in fluid communication with annular groove
76, and is configured to direct a distinctive stream of gas from
groove 76, through passage 63 and into the ambient atmosphere
surrounding the outlet from extrusion passage 65. More
particularly, the present invention is constructed and arranged to
produce a gas stream having both an axial velocity component as
well as a circumferential velocity component.
For the purposes of the present description, the axial direction is
along the axis of nozzle body 50, and typically is along the
direction defined by extrusion passage 65. The circumferential
direction is perpendicular to the axial direction and substantially
tangential to a circle which is substantially centered on orifice
82.
The resultant gas stream around extrusion passage 65 can operate to
entrain the stream of hot-melt adhesive issuing forth from
extrusion passage 65, and to impart a generally circular, swirling
motion to the molten adhesive stream after the adhesive has exited
from the passage. The adhesive stream advantageously remains in the
form of a substantially continuous filament traveling along a
generally helical path. The helical path has an expanding diameter,
and the expansion can be selectively controlled by adjusting the
configuration of nozzle unit 24.
In a particular aspect of the invention, the swirling gas stream
and the supplied air pressure are configured and arranged to
entrain the stream of hot-melt adhesive and impart at least about
300 swirls per second. Preferably, the invention imparts about
400-600 swirls per second to the adhesive stream, and more
preferably, the invention imparts about 500 swirls per second to
provide improved control of the adhesive deposition pattern.
The present invention can advantageously provide desired adhesive
patterns while employing relatively low air pressures and
relatively low gas stream velocities. In particular, the invention
can operate effectively while employing air pressures within the
range of about 15-30 psi (about 103-207 kPa). In addition, the
invention can operate effectively while employing gas velocities of
not more than about 6000 feet/minute. In one aspect of the
invention, the method and apparatus are configured to operate with
the gas steam exiting from gas passage 63 at a velocity of about
3,000 feet/minute.
In the illustrated embodiment housing member 78 engages threads
formed on the outer surface of head portion 58. It is readily
apparent, however, that other fastening systems may also be
employed to attach or otherwise interconnect the housing member and
the nozzle head portion. As representatively shown in FIG. 6,
housing member 78 includes an annular ridge member 79 which extends
outwardly and longitudinally from an end face of the housing
member, and extends along a circumferential edge section of the
housing member. Ridge member 79 also extends radially inward toward
extrusion passage 65 and terminates at a position which is spaced
from the extrusion passage by a selected radial distance 77. In the
shown embodiment, this radial spacing distance is within the range
of about 0.521-0.625 cm, and preferably is about 0.607 cm. Ridge
member 79 also extends longitudinally along the axial dimension of
nozzle body 50 by a selected distance 75, which in the shown
embodiment is within the range of about 0.07-0.11 cm, and
preferably is about 0.09 cm. As a result, ridge member 79 delimits
a substantially cylindrical recess or chamber 81 into which gas
passage 63 and extrusion passage 65 exit. The chamber has a radius
77 and a length 75. The inward facing wall surface 30 of the ridge
member may optionally be configured with a bevel angle 150 to
increase or decrease the diameter of the adhesive swirl pattern
formed on the substrate. For example, increasing the bevel angle
can increase the rate of expansion of the swirling adhesive
filament to form a larger diameter swirl pattern. In a particular
aspect of the invention, the bevel angle is within the range of
about 0-60.degree. and in the shown embodiment the bevel angle is
about 45.degree.. In the shown embodiment, the exit region of
nozzle 80 at orifice 82 is positioned substantially flush with the
immediately adjacent edge of chamber 81 defined by housing 78. In
an optional arrangement, nozzle section 80 may be configured such
that the exit of nozzle 80 protrudes into chamber 81 by a distance
which is within the range of about 0.005-0.007 inches (about
0.013-0.015 cm).
To maintain the desired, substantially continuous configuration of
filament 11, nozzle unit 24 is configured to be substantially free
of gas streams or other mechanisms which might disrupt the
continuity of the swirling filament of work material. As a result,
the present invention can advantageously impart a swirling motion
to filament 11 while substantially avoiding a breaking or
disintegration of the filament. As a result, a substantially
continuous swirled filament of work material can be deposited onto
the selected substrate.
It has been found that various factors can affect the diameter of
the deposition pattern. Such factors include, for example, the
air-to-adhesive ratio, the adhesive viscosity and the distance
between nozzle section 80 and web 14. Accordingly, it is
contemplated that some adjustments to the system will need to be
made depending upon the physical properties of the adhesive or
other work material being deposited onto web 14.
It has also been found that the size and diameter of the deposition
pattern can be effectively regulated by controlling the dimensions
of chamber 81. In particular, the rate of radial expansion of the
path of the swirling adhesive stream can be adjusted by selectively
increasing or decreasing the axial length dimension 75 of chamber
81. For a given distance between nozzle unit 24 and web 14,
increasing the axial length dimension can reduce the rate of
expansion and produce a deposition pattern having a relatively
narrower width 91 (FIG. 11). Decreasing the axial dimension can
increase the rate of expansion and produce a deposition pattern
having a relatively greater width. With the shown embodiment of the
invention, for example, the axial length 75 of flange member 79,
and thus the axial length of chamber 81, is adjusted to be within
the range of about 0.076-0.10 cm. to expand the path of the
adhesive stream at a rate sufficient to allow placement of web 14
at a distance of about 2.5-3.5 cm. from the exit of extrusion
passage 65 in nozzle unit 24, while still providing a deposited
adhesive pattern width 91 of at least about 1.2 cm.
The distinctive configuration of the present invention can
advantageously improve the system tolerance to start-up conditions.
During start-up, there is relatively more air and relatively less
adhesive than during normal running conditions. With conventional
systems, excessive amounts of adhesive may be drawn up onto the
nozzle unit, thereby fouling the nozzle and interfering with the
formation of desired adhesive deposition patterns. Such
difficulties can be reduced by employing the present invention.
With reference to FIG. 7, nozzle unit 24 may advantageously be
configured to reduce the dripping or drooling of molten work
material during those periods of time when the operation of the
nozzle unit is shut down. With this particular aspect of the
invention, a forcing means such as spring 124 is disposed within
nozzle body 50 the forcing means resiliently urges a valving member
126 against a valve seating member 128 to selectively block the
flow of work material through nozzle body 50. In the illustrated
embodiment, work material supply passage 64 is enlarged to form a
valving chamber 130 which is suitably sized to accommodate spring
124. One end of the spring engages a bottom wall section of chamber
130 and the opposite end of the spring engages valve member 126.
Valve seat member 128 is assembled into the open end of chamber
130, and in the shown embodiment is secured to nozzle body 50 with
a threaded engagement. It is readily apparent that other fastening
systems may also be employed. Valve seat member 128 includes a bore
channel 129 extending axially therethrough for conducting work
material into valve chamber 130, through which the work material
passes into supply passage 64. When valve seat member 128 is
assembled into nozzle body 50, the valve seat engages valve member
126 to form an operable seal therebetween. The insertion and
assembly of valve seat member 128 is configured to compress spring
124 by a selected amount to provide a closure force within the
range of about 0.25-1.0 pounds. The spring constant within spring
124 and the amount of compression of the spring are selected to
provide the desired amount of closure force. The closure force is
great enough to form an effective seal between valve member 126 and
valve seat 128 but is low enough such that the work material under
an applied pressure of about 100 psi (about 689 kPa) is sufficient
to displace valve member 126 away from valve seat 128 and allow the
passage of molten work material into valve chamber 130. As a
result, when pressure is applied to the supply of work material the
valving system will open and allow the extrusion filamentary
material from extrusion passage 65. When the pressure to the work
material is sufficiently reduced, spring 124 can urge the valving
system closed and stop the supply of molten material into chamber
130. As a result, at those times when the supply of molten material
is intended to be cut off, the undesired dripping and drooling of
molten material from extrusion passage 65 can advantageously be
reduced.
During the operation of a representative system, the selected
hot-melt adhesive is heated to its molten state and supplied from a
conventional reservoir. Suitable adhesives can include, for
example, 34-5522 or 34-5510 adhesive supplied by National Starch
and Chemical Corp., or other hot-melt adhesives having equivalent
properties. The adhesive is heated to a temperature sufficient to
allow the molten adhesive to be pumped and extruded through the
nozzle units. In the illustrated embodiment, the hot-melt adhesive
is heated to a temperature of about 275-400.degree. F. (about
135-204.degree. C.), and the molten adhesive is metered and pumped
through suitable conduits and delivered to transfer plate 44.
Referring to FIG. 12, a conventional single-stream metering pump 31
delivers molten adhesive from a reservoir tank 17 through supply
line 37 to a common manifold 45 located at nozzle assembly 10. Pump
31 is suitably sized and configured to supply and pressurize the
adhesive held in manifold 45. Excess pressure in manifold 45 is
released through pressure relief valve 35, which directs and
recirculates the released adhesive through adhesive return line 39
back to the reservoir tank. In the shown embodiment, the relief
valve is adjusted to maintain in manifold 45 an adhesive pressure
which is within the range of about 10-35 psi.
A plurality of conventional pumps draw molten adhesive from
manifold 45, and deliver individual metered streams of adhesive to
each nozzle unit 24. The shown embodiment of the invention employs
a plurality of multistream metering pumps 33, which are configured
to deliver individual selected amounts of molten adhesive at
predetermined rates to the nozzle units. More particularly, each
multistream metering pump 33 can be a commercially available,
four-stream metering pump which is capable of delivering precisely
measured amounts of adhesive through independent porting and
conduits to transfer plate 44, and then through independent
conduits 84 to four individual nozzle units. For example, the shown
embodiment of the invention employs six, four-stream metering pumps
33 to supply molten adhesive to two nozzle banks 20, 22, wherein
each nozzle bank comprises twelve individual nozzle units 24. It is
readily apparent, however, that additional metering pumps could be
employed to supply adhesive to additional nozzle units. Also,
different size metering pumps 33 could be employed configured to
deliver greater or less than four metered streams from each pump.
Any such changes or modifications are contemplated as being within
the scope of the invention.
If one or more of the metered streams of adhesive goes to a nozzle
location which has been closed with a plug 100 (FIG. 5), adhesive
will travel through return ports 62, through transfer plate 44 into
manifold 45, and then recirculate to reservoir 17. Similarly, if a
nozzle unit should become plugged, the nozzle unit includes a
mechanism for venting excess pressure and adhesive through adhesive
return ports 62.
The configuration of the invention can advantageously provide a
substantially uniform and substantially equalized flow of adhesive
from each of the nozzle units. The invention can also provide a
more precise control of the adhesive deposition patterns onto the
chosen substrate. In one aspect of the invention, the flow rate of
adhesive from each of the nozzle units can be regulated to have a
variation of not more than about plus or minus 5%. In further
aspects of the invention, the adhesive flow rate is preferably
controlled to have a variation of not more than about plus or minus
2%, and more preferably, is controlled to have a variation of not
more than about plus or minus 1% to provide improved performance.
Thus, the invention can produce a more uniform array of adhesive
deposition patterns over the surface of the substrate, and the
resultant, more uniform distribution of adhesive add-on can thereby
produce more uniform bonding of the final product with improved
product integrity.
Suitable metering pumps for use with the invention are manufactured
by various commercial vendors. The four-stream metering pump 33
can, for example, comprise an Acumeter MBE-HA manifold pump coupled
to a #15747 front-pump mechanism and a #15668 drive-pump mechanism.
The various pump mechanisms can be connected to an Acumeter
assembly which provides a manifold for incoming adhesive and
provides a distribution system for the individual streams of
adhesive metered from the pump mechanisms. Acumeter, Inc. is a
company having facilities in Marlborough, Mass.
Typically, metering pumps 33 can deliver hot-melt adhesive at a
pressure of not more than about 1000 psi (about 6894 kPa). In the
illustrated embodiment, metering pumps 33 deliver hot-melt adhesive
to the transfer plate and nozzle units at a pressure within the
range of about 250-750 psi (about 1724-5170 kPa). The liquid
hot-melt adhesive flows from the metering pumps into transfer plate
44 through porting located in manifold 45 and then through passages
84 into nozzle plate 32, where the adhesive is introduced into the
individual bore holes 48. From bore 48, the molten adhesive flows
into supply passage 64 and proceeds through nozzle body 50 into
extrusion passage 65 of head button 80. The molten adhesive is then
expelled through each of the individual nozzle units 24 in a
generally continuous stream. In a particular aspect of the
invention, the molten adhesive is delivered from each nozzle unit
at a flow rate of about 2-20 gm./min. Preferably, the molten
adhesive is delivered at a rate of about 9-15 gm./min., and more
preferably is delivered at a rate of about 12.3 gm./min. to provide
an improved deposition pattern.
To provide improved process control, FIG. 3 representatively shows
an embodiment in which nozzle plate 32 is heated with a suitable
heating mechanism 34, such as a Model E1078 heater produced by
Acumeter, Inc. The heater is adjusted to maintain the nozzle plate
at a temperature of about 270-400.degree. F. (about 132-204.degree.
C.), and more preferably is maintained at a temperature within the
range of about 290-320.degree. F. (about 143-160.degree. C.) to
provide improved processing. A conventional thermostat 29 can be
employed to help regulate the temperature. Since the nozzle plate
is in close contact with transfer plate 44 and nozzle units 24, it
will be readily apparent that heater 34 can operably heat the
transfer plate and nozzle units, as well as the nozzle plate. While
the shown embodiment incorporates three heaters 34, other numbers
of individual heating units may also be employed.
As the hot-melt adhesive is extruded from the nozzle units, heated
air is introduced into transfer plate 44 through gas inlet 36 (FIG.
3) from a conventional supply 19 (FIG. 13) of pressurized air. A
suitable device 41 for heating the air is a Model GCH-1XT
manufactured by Chromalox located in Ogden, Utah. In the
illustrated embodiment of the invention, the air is heated to a
temperature of about 250-400.degree. F. (about 121-204.degree. C.),
and preferably is heated to a temperature of about 290-320.degree.
F. (about 143-160.degree. C.) to provide improved process control.
The heated air is conducted into nozzle plate 32 and delivered to
gas inlet port 68, as shown in FIG. 4. From the gas inlet port, the
heated air passes through the expanded region 70 of bore 48 and
then into gas passage 74, through which the air is introduced into
the transfer space defined by groove 76. The air then passes
through outlet passage 63 which directs the gas into an airstream
having both a circumferential velocity component and an axial
velocity component. The resultant airstream operably engages and
entrains the stream of molten adhesive issuing forth from the exit
of extrusion passage 65, and operably imparts a swirling, generally
circular component of motion to the liquid adhesive stream. In a
particular aspect of the invention, the airstreams are configured
to cooperate and operably entrain the adhesive stream without
excessively disrupting its substantially continuous, filamentary
configuration. Consequently, as the molten adhesive moves toward
substrate web 14, the adhesive stream traverses along a generally
spiral or helical path having both a circumferential as well as an
axial component of motion.
With reference again to FIG. 1, the invention is configured to move
substrate web 14 at a selected speed along a predetermined machine
direction 27 of the apparatus. As a result, the adhesive stream can
be deposited onto web 14 in a curvilinear pattern. The deposited
pattern of adhesive can be adjusted by regulating the movement
speed of web 14, by regulating the circumferential and axial
velocity components imparted to the adhesive stream, and by
adjusting the distance between nozzle section 80 and web 14.
The technique of the present invention includes suitable driving
means, such as electric motors (not shown), for rotating the
conveyor rollers at a speed sufficient to impart a desired
transporting speed to web 14. High web speeds are desired to
improve manufacturing efficiency, but at high web speeds,
conventional adhesive spraying systems have not been able to
maintain satisfactory control over the adhesive deposition
patterns. In contrast to such conventional techniques, the method
and apparatus of the present invention can produce accurate
adhesive deposition patterns at web speeds of at least about 350
ft./min. In further aspects of the invention, sufficiently accurate
and precise control of the deposition patterns can advantageously
be maintained at web speeds of at least about 450 ft./min. and even
at web speeds of at least about 600 ft./min. The shown embodiment
may, for example, provide a web speed of about 800 ft./min. and may
further provide a web speed of up to about 1,000 ft./min.
In a particular aspect of the invention, the method and apparatus
can be adjusted to deposit each individual stream of hot-melt
adhesive swirled into a looping, semi-cycloidal pattern. In the
general sense, a cycloid is the path traced by a point on the
peripheral circumference of a wheel as the wheel rolls over a flat
surface without slippage. If, however, there is slippage between
the surface and the rolling wheel, the point on the circumference
of the wheel will trace a path having a retroceding section which
forms a loop in the traced path. The semi-cycloidal pattern
representatively shown in FIG. 10 is similar in form to the path
traced by the point on the wheel where the wheel is rolling with
slippage. As a result, each semi-cycloidal pattern has a
retroceding loop section 92 traced by the deposited hot-melt
adhesive.
It has been discovered that a generally continuous, semi-cycloidal
pattern of adhesive can be produced by suitably controlling the air
pressure supplied to the individual nozzle units. Accordingly, a
particular aspect of the invention includes a gas pressure
regulator 18, such as a Model R11 manufactured by C. A. Norgren Co.
having facilities in Littleton, Colo. The pressure regulator is
constructed to be capable of delivering about 80 psi (about 551
kPa) of air pressure. In a particular aspect of the invention, the
pressure regulator is configured to provide not more than about 32
psi (about 221 kPa) of air pressure, and preferably is configured
to provide air pressure within the range of about 12-32 psi (about
82.7-221 kPa). In the shown embodiment, about 25 psi (about 172
kPa) of air pressure is provided to the nozzle unit. Too low an air
pressure, such as a pressure below about 12 psi (about 82.7 kPa),
may not produce the desired loop deposition pattern at the selected
adhesive throughput rate. Instead, the pattern can have the
appearance of a wavy line and can provide inadequate distribution
and coverage of adhesive over the surface area of the substrate. If
the supplied air pressure is too high, the deposited pattern of
adhesive may suitably cover the surface of the web, but the
airstreams can excessively scatter the positioning of the adhesive.
As a result, the cross-directional positioning of the adhesive will
be inaccurate and there can be excessive overspray which would
contaminate the equipment and waste adhesive.
A particular aspect of the invention can include separate, gas
pressure regulators for nozzle banks 20 and 22, as representatively
shown in FIG. 13. Such an arrangement may be especially useful when
the individual nozzle banks have unequal numbers of nozzle units
24. For example, first nozzle bank 20 may have thirteen nozzle
units, and second nozzle bank 22 may have twelve nozzle units. In
such a situation, the separate gas flow regulators may be adjusted
to supply different amounts of gas to the different nozzle banks.
More particularly, less gas could be supplied to the nozzle bank
having fewer nozzle units to fine tune the system.
In the embodiment shown in FIG. 13, air or other suitable gas is
delivered from a designated gas supply 19 through control valve 18
into gas heater 41. The heated air then travels through an
insulated supply line 43 to a distribution manifold 73 which splits
the heated air into four individual air streams. Two air streams
are directed to nozzle plate 32 through air conduits 49 and 51 to
supply heated air to nozzle bank 20. Two other air streams are
directed to the nozzle plate through air conduits 53 and 55 to
supply heated air to second nozzle bank 22. Gas flow control valves
57 and 59 are constructed and arranged to regulate the flow of
heated air through conduits 49 and 51, respectively.
It has also been discovered that the distance between nozzle units
24 and web 14 is an important parameter for providing the desired
semi-cycloidal deposition pattern. Accordingly, in one aspect of
the invention, the distance between the exits from nozzle extrusion
passages 65 and the position of web 14, as it moves over rollers
16, is limited to a maximum separation distance 98 (FIG. 1A) of
about 2 in. Preferably, the separation distance is not more than
about 1.75 in., and more preferably, the separation distance is
within the range of about 1.0-1.5 in. to provide improved control
over the deposition patterns. The reduced separation distance, for
example, can reduce the chances of disrupting the desired
deposition patterns with extraneous side currents of air or other
windage.
With the shown embodiment of the invention, the semi-cycloidal
pattern from each nozzle has a cross-directional extent or width 91
(FIG. 11) of about 0.5-0.75 in. (about 1.27-1.9 cm.). In addition,
the individual spacing 95 between adjacent loops of the adhesive
pattern, as measured along the machine direction, is within the
range of about 0.5-2.0 cm. Preferably, the machine direction
spacing between loops is about 0.7-1.4 cm., and more preferably is
about 0.8-1.0 cm. to provide improved bonding characteristics. If
the spacing is too small, an excessive amount of adhesive will be
expended, and if the spacing is too great, the adhesive pattern may
provide inadequate bonding strength.
In one aspect of the invention, the method and apparatus are
constructed and arranged to form an array composed of a plurality
of juxtaposed, semi-cycloidal patterns of hot-melt adhesive, as
representatively shown in FIG. 11. In a further aspect of the
invention, the juxtaposed semi-cycloidal patterns are arrayed in a
configuration wherein two or more adjacently located,
semi-cycloidal patterns contact each other along adjacent marginal
side sections 94, 96 thereof. For example, the adjacently located
patterns of hot-melt adhesive may contact each other along a
substantially continuous line which extends along machine direction
27 of web 14. Accordingly, the plurality of semi-cycloidal patterns
illustrated in FIG. 11 contact one another along substantially
continuous, generally parallel lines which extend along the
longitudinal, machine direction 27.
To produce the desired array of adhesive patterns on web 14, a
plurality of nozzle units are selectively positioned along the
cross-direction 26 of the apparatus. More specifically, the
incorporation of each additional nozzle unit can effectively add
another semi-cycloidal pattern of adhesive and thereby
incrementally increase the cross-directional width of web 14 which
is covered with adhesive.
It has, however, been discovered that a conventional, linear
arrangement of the individual nozzle units 24 along cross-direction
26 may not produce the desired deposition array of adhesive. It has
been found that the group of airstreams issuing forth from one
nozzle unit 24 would excessively interfere with the group of
airstreams issuing forth from an adjacent nozzle unit. As a result,
the desired array of juxtaposed semi-cycloidal patterns can be
disrupted and the bonding effectiveness can be excessively
reduced.
One technique for addressing this problem has been to increase the
cross-directional spacing between adjacent nozzle units. Such a
technique, however, can leave undesirable gap regions between
adjacent patterns of deposited adhesive. The gap regions would then
be unbonded to the completed assembly, and would have lower
strength and poorer integrity.
The structure and arrangement of the present invention provides an
improved configuration which more effectively reduces the
interaction between adjacent groups of airstreams and more
effectively reduces the interference between adjacent streams of
adhesive. In particular, the invention can be advantageously
configured with the nozzle units 24 arranged in the alternating,
offset and staggered arrangement previously discussed with
reference to FIG. 2. As representatively shown in FIG. 2, the
individual nozzle units 24 are grouped into a first nozzle bank 20
and a second nozzle bank 22. Within first nozzle bank 20, for
example, the adjacent nozzle units 24a and 24b are spaced apart by
a cross-directional distance which is sufficient to substantially
prevent adjacent groups of airstreams from interfering with each
other, and also to substantially prevent adjacent swirling streams
of hot-melt adhesive from interfering with each other as they
traverse from the nozzle units to the web substrate. Accordingly,
the cross-directional separation 88 between adjacent nozzle units
24a and 24b should be not less than about the average of the widths
91a, 91b (FIG. 11) of the associated, adjacent semi-cycloidal
patterns produced by these nozzle units. In the shown embodiment,
the cross-directional spacing between nozzle units 24a and 24b is
approximately equal to two times the width 91 of one of the
semi-cycloidal patterns 90. FIG. 2 representatively shows a
particular nozzle bank having individual nozzle units 24 which are
substantially equally spaced along the cross-direction, but an
unequal cross-directional spacing between adjacent nozzle units
could also be employed.
The configuration of second nozzle bank 22 is similar to the
configuration of first nozzle bank 20. The second nozzle bank,
however, is offset from the first nozzle bank along the machine
direction by an offset distance 23 sufficient to substantially
prevent the airstreams from the first nozzle bank from interfering
with the airstreams from the second nozzle bank, and to
substantially prevent the motions of the adhesive streams from the
first nozzle bank from interfering with the motion of the adhesive
streams produced by the second nozzle bank. In the illustrated
embodiment, the machine direction offset 23 is at least about 3.0
cm., and preferably is at least about 4.0 cm. to provide improved
performance.
In addition to being offset in the machine direction, the nozzle
units in second nozzle bank 22 are staggered in the cross-direction
relative to the nozzle units in first nozzle bank 20. As can be
seen in FIG. 2, the individual nozzle units comprising second
nozzle bank 22 are positioned in the cross-directional gaps which
separate the individual nozzle units comprising first nozzle bank
20. As a result, the nozzle banks 20, 22 in combination can provide
a substantially complete coverage of adhesive over web 14 while
substantially preventing undesired interaction or interference
between the air streams and adhesive streams produced by the
individual nozzle units 24. The invention can thereby
advantageously provide a consistent deposition pattern from each of
the nozzle units 24, and can provide a more accurate
cross-directional positioning of the adhesive patterns on web 14.
In one aspect of the lateral side edge 94 of one or more of the
semi-cycloidal adhesive patterns 90 has a cross-directional
variation of not more than about plus or minus 0.125 in. relative
to a predetermined desired position along the cross-direction.
Preferably, the cross-directional positioning variation is not more
than about plus or minus 0.063 in., and more preferably is not more
than about plus or minus 0.032 in. to provide improved
performance.
The offset and staggered relationship between first nozzle bank 20
and second nozzle bank 22 can also provide the capability to
selectively adjust an amount of overlap 93 (FIG. 11) between
adjacent, semi-cycloidal patterns of adhesive. For example, the
individual nozzle units within first nozzle bank 20 can have
substantially equal cross-directional separations 88 which are
between about 1-2 times an average pattern width 91. The individual
nozzle units within second nozzle bank 22 can then be configured
with similar cross-directional separations, and the second nozzle
bank can be offset in the machine direction from the first nozzle
bank. In addition, the nozzle units within second nozzle bank 22
can be staggered with respect to the nozzle units within first
nozzle bank 20. Stagger distance 87, for example, can be adjusted
to be about one-half of separation distance 88, and the apparatus
can be arranged to have the nozzle units produce adhesive patterns
of substantially equal width 91. As a result of this particular
configuration, the apparatus can produce an array of multiple,
semi-cycloidal adhesive patterns wherein the adjacent patterns
overlap by a discrete distance 93. For example, a particular aspect
of the invention provides an overlap distance 93 within the range
of about 0.125-0.25 in. (about 0.32-0.63 cm.) to thereby produce a
desired combination of good bonding strength and economy of
adhesive add-on.
The illustrated embodiment of the invention representatively shows
a configuration wherein the nozzle units that respectively form
immediately adjacent deposition patterns are arranged in a
substantially "zig-zag" layout. In an alternative embodiment of the
invention, the desired offset and staggered arrangement of the
individual nozzle units may be accomplished by positioning three or
more nozzle units substantially along a line which extends
diagonally across the machine-cross direction. A nozzle bank having
such a construction could be rotated to adjust the angle of the
diagonal to control the amount of overlap 93 between adjacent
deposition patterns 91.
Another advantage afforded by the present invention is an ability
to incrementally reduce the total width of the area covered by the
array of deposited adhesive patterns. More particularly, the total
width of the web area, which is occupied by the deposited adhesive
can be adjusted by selectively removing nozzle units and capping
off the corresponding, associated bore holes 48 with a plug
mechanism 100.
As representatively shown in FIG. 5, plug 100 is substantially
cylindrical in shape and includes an annular flange 102 formed at
one end thereof. Flange 102 is constructed and arranged to
sealingly engage surface 54 of nozzle plate 32 and to effectively
cover the opening of the bore hole 48. Gasket member 40 provides a
substantially airtight seal between surface 54 and flange 102. The
gasket is composed of a conventional fibrous gasket material, and
is configured to reduce air leaks caused by irregularities in the
mating surfaces. A cylindrical body section 104 of the plug extends
into bore 48 and includes a circular groove configured to
accommodate therein a sealing means, such as O-ring 108. O-ring 108
is positioned between adhesive return port 62 and the expanded
region 70 of bore hole 48. In addition, the axial length of plug
body 104 is selected so as to stop short of the position of
adhesive return port 62. As a result, hot-melt adhesive is able to
recirculate from bore 48 through adhesive return port 62 and return
to a suitable reservoir accumulator.
In a further aspect of the invention, the method and apparatus
include a pressure release means for relieving excessive pressure
built up behind a partially or completely plugged nozzle orifice.
Referring to FIG. 4, O-ring 61 is constructed and arranged to
bypass excessive pressure which might build up behind a plugged
nozzle orifice. In particular, O-ring 61 is constructed and
arranged to operably deflect to allow the passage of pressurized
adhesive from bore hole 48 past the position of O-ring 61 and into
adhesive return port 62. In the illustrated embodiment, O-ring 61
is constructed to operably deflect when subjected to an adhesive
pressure of more than about 1400 psi. As a result of the
configuration of O-ring 61 and the positioning of adhesive return
port 62, the invention can substantially prevent the undesired
backing of adhesive into the air system comprising expanded section
70 and gas inlet port 68. The distinctive configuration of the
invention can thereby reduce unanticipated maintenance of the
system.
The present invention can be employed to produce distinctive
manufactured articles, such as disposable garments, infant diapers,
feminine care products, incontinence products and other adhesively
bonded assemblies. More particularly, the present invention can be
employed to produce distinctive absorbent articles, such as
disposable diaper 110.
With reference to FIG. 14, disposable diaper 110 includes an outer
layer 112, a bodyside layer 114 and an absorbent body 116
sandwiched between the outer and bodyside layers. The outer and
bodyside layers extend outwardly past the side edges of absorbent
body 116 to form side seals and side flaps or cuffs, which are
constructed to contact and sealingly engage the thighs of the
wearer. In certain arrangements, leg elastics are positioned in the
side flaps to produce elasticized gathers, which can provide
improved sealing and leakage prevention around the wearer's legs
and improved fit. In addition, the outer and bodyside layers may
extend beyond the longitudinal edges of absorbent body 116 to form
waistband portions of the diaper, and waist elastics 120 may be
assembled into the waist band portions. Absorbent body 116 may
comprise one or more layers of high wet-strength tissue wrapped
around an absorbent core composed of a mixture of woodpulp fluff
and superabsorbent particles. A representative diaper article is
described in U.S. Pat. No. 4,699,823 issued Oct. 13, 1987 to S.
Kellenberger, et al., which is hereby incorporated by reference to
the extent it is consistent with the present disclosure.
Diaper 110 includes an array of adhesive arranged to secure one or
more of the layers to the absorbent body. The adhesive array is
distinctively composed of a plurality of juxtaposed, semi-cycloidal
patterns of adhesive which extend substantially along a
longitudinal dimension of the article. For example, outer layer 112
may be secured to absorbent body 116 by the array of semi-cycloidal
patterns of adhesive. Alternatively, the array of adhesive may be
employed to secure bodyside layer 114 to the absorbent body.
Similarly, the array of adhesive may operably secure outer layer
112 to bodyside layer 114, or secure the tissue wrap to the
absorbent core. In the illustrated embodiment, an adhesive array
composed of a plurality of juxtaposed, semi-cycloidal patterns of
adhesive is applied with the adhesive patterns extending
substantially along the lengthwise dimension of the article. In
addition, the adjacent patterns of the adhesive contact each other
along adjacent, marginal side portions of the semi-cycloidal
patterns. The shown embodiment of diaper 110 includes adjacent
patterns of adhesive which contact each other along substantially
continuous, generally parallel lines which extend along the
longitudinal dimension. Alternatively, the adjacent semi-cycloidal
patterns may overlap each other along the side margins of the
individual patterns.
The amount of adhesive distributed over outer layer 114 is within
the range of about 1.0-6.0 gm. per square meter. Preferably, the
amount of adhesive add-on is within the range of about 4.0-5.0 gm.
per square meter to provide more improved efficiency. When compared
to the amount of adhesive add-on employed with construction
adhesive applied in the pattern of generally linear, parallel lines
of adhesive, the amount of adhesive incorporated into the
distinctive patterned array of the invention can be decreased to
about 50% of the conventional amount of adhesive. Even though the
amount of adhesive employed is reduced, the distinctive adhesive
distribution provided by the present invention can adequately
maintain the integrity of the final product. In particular, when
compared to the conventional, parallel adhesive line construction
technique, the bonding strength at end seal region 122 can be
substantially maintained even though the amount of adhesive add-on
is reduced. For example, the amount of adhesive may be reduced from
about 0.94 gm./diaper to about 0.54 gm./diaper and still maintain
approximately the same end seal strength. In addition, the
distribution of the adhesive in the distinctive patterns and arrays
of the invention can advantageously provide a more flexible outer
cover layer which has a more pleasing cloth-like appearance and
feel.
A representative comparison of the end seal strengths and the
amount of adhesive add-on is set forth in the graph shown in FIG.
15. The graph representatively shows data generated from
medium-size disposable diapers, constructed with a conventional
hot-melt construction adhesive. More particularly, the diapers were
constructed with National Starch 34-5522 or 34-5510 adhesive. When
compared to conventional, generally parallel adhesive lines, the
looping-type adhesive patterns produced in accordance with the
present invention can advantageously provide increased end-seal
strengths at the same amounts of adhesive add-on. Alternatively,
the adhesive patterns produced in accordance with the present
invention can advantageously provide the same end-seal strengths
with lower amounts of adhesive add-on.
For the purposes of the present invention, the following procedure
is a suitable technique for determining the end seal strength:
A test specimen is prepared by cutting a rectangular sample
measuring 3 in..times.5 in. from the center of the waistband
section of the diaper. One 3 in. side of the sample corresponds to
the terminal waistband edge, and the two 5 in. sides extend along
the longitudinal length of the diaper. The fluff pad material is
then removed from the sample without disturbing the patterns of
adhesive in the end seal region of the sample. The end seal region
is the portion of the sample wherein the bodyside liner is
adhesively bonded or otherwise attached and laminated with the
outer cover layer. The end seal strength corresponds to the force
required to peel apart the bond between the liner and outer cover,
and is expressed in terms of peak load measured in grams
(gram-force). The apparatus employed to measure the end seal
strength is an Instron tensile tester with a 10 kilogram load cell,
or equivalent tensile testing apparatus, in conjunction with a
Microcon microprocessor apparatus. The Microcon device analyzes
input data to provide, for example, load vs. elongation plots and
Total Energy Absorption information from the test sample, and is
distributed by Instron Corp. having facilities at Canton, Mass. The
Instron tensile test apparatus is set with a cross-head speed of 10
inches per minute and a chart speed of 2 inches per minute. The jaw
spacing of the Instron apparatus is set at 4 inches. The Microcon
apparatus is initialized to the following set of conditions:
Initial sample length=4inch (gauge length)
Cross-head speed=250mm/min.
Automatic return=10inch
Print mode=peak load, break energy
The test sample will have a generally "Y" configuration wherein the
end seal portion corresponds to the base of the Y, the liner
material corresponds to one arm of the Y, and the outer cover
material corresponds to the second arm of the Y. The two arms of
the sample are secured in the jaws of the Instron apparatus with
the inside of the sample facing toward the front of the Instron
apparatus and the outer cover material held in the moveable jaw.
The line of separation between the outer cover material and the
liner material is positioned approximately half way between the two
jaws. The cross-head motion of the Instron machine is then started,
and when the sample has been completely peeled apart, the highest
average peel force applied to the test sample is recorded.
Having thus described the invention in rather full detail, it will
be readily apparent that various changes and modifications may be
made without departing from the spirit of the invention. All of
such changes and modifications are contemplated as being within the
scope of the invention, as defined by the subjoined claims.
* * * * *